Field of the Invention
The present invention relates to a liquid ejection module and a liquid ejection head used to eject a liquid such as ink.
Description of the Related Art
In a recent inkjet printing apparatus, liquid ejection elements are densely provided in a liquid ejection head in order to print a high-quality image at a higher speed. In such a liquid ejection head, since passages are densely arranged compared with the related art, the passages are decreased in size.
When the passage is decreased in size, a flow resistance increases when the liquid flows therethrough and thus pressure loss increases. For this reason, a negative pressure at an ejection opening increases and thus a printing operation may be influenced. For example, when the negative pressure increases, a meniscus of the ejection opening is retracted toward the inside of the ejection opening and thus a liquid ejection amount becomes smaller than that of a low negative pressure state. When the liquid ejection amount is small, printing density becomes low and thus a desired result cannot be obtained.
Here, U.S. Pat. No. 7,845,763 discloses a print head assembly capable of printing an image at a high speed while suppressing pressure loss caused by a flow resistance to minimum by employing a structure in which a liquid is supplied through a large passage extending as close as possible to a print element and is supplied through a fine passage formed in the vicinity of the print element.
When the large passage is connected to the fine passage, a negative pressure is low at the ejection opening which is relatively close to the connection position, but increases as it goes away from the connection portion. In the structure disclosed in U.S. Pat. No. 7,845,763, supply openings for different ejection opening rows are provided at the same position in a print medium conveying direction. Thus, since the ejection opening having a low negative pressure and the ejection opening having a high negative pressure in each ejection opening row are located at the same position in the conveying direction, shade caused by printing density (unevenness in printing) occurs at the same position of the ejection opening row and thus the shade is emphasized and easily recognized.